The present invention relates to a DC-DC converter and, more particularly, to a single inductor, multiple output DC-DC converter.
Single inductor, multiple output, DC-DC converters that generate two different DC output voltages using a single inductor are known, for example in U.S. Pat. Nos. 6,204,651 and 6,977,447.
FIG. 4 of the '447 patent shows a single-inductor, multiple-output, DC-DC boost converter. The boost converter alternates between phases in which energy is transferred from a battery to the inductor and phases in which energy is transferred from the inductor to one of two capacitors that generate the two DC output voltages. In addition, the boost converter alternates between periods of charging the first capacitor associated with the first DC output voltage and periods of charging the second capacitor associated with the second DC output voltage based on which of the two DC output voltages is relatively most deficient compared to its desired voltage level.
FIG. 6 of the '447 patent shows a single-inductor, multiple-output, DC-DC buck converter. The buck converter alternates between a phase in which the inductor and one of two capacitors that generate the two DC output voltages are charged by the battery and a phase in which the inductor is discharged. In addition, the buck converter alternates between periods of charging the first capacitor associated with the first DC output voltage and periods of charging the second capacitor associated with the second DC output voltage based on which of the two DC output voltages is relatively most deficient compared to its desired voltage level.
In both converters, the duty cycle of the charge signal that controls the energizing of the inductor is regulated based on the common-mode voltage of the two DC output voltages.